JP2005302106A - Prism and optical pickup device using the same, and optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prism capable of reducing a manufacturing man-hour, an optical pickup device using the same, and an optical system. <P>SOLUTION: In the optical pickup device 1 equipped with a PBS prism 8 which is provided with 1st-3rd transparent members 8a, 8b and 8c having bonded surfaces 8m, 8p, 8q and 8n inclined with respect to parallel two faces for adhering both bonded faces 8m, 8p of the 1st and 2nd transparent members 8a, 8b through a PBS film 8d and also for adhering both bonded faces 8q, 8n of the 2nd and 3rd transparent members 8b, 8c through a PBS film 8e, the PBS prism 8 is formed in point symmetry by making a distance L2 between the end face 8k of the 3rd transparent member 8c and the PBS film 8e equal to a distance L1 between the end face 8j of the 1st transparent member 8a and the PBS film 8d. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a prism having an optical thin film that reflects incident light, an optical pickup device using the prism, and an optical system.

  An optical disc apparatus that reproduces or records an optical disc such as a CD or a DVD reads and writes signals using light of different wavelengths depending on the medium. Patent Document 1 discloses an optical pickup device that reads an optical disk. This optical pickup device has a plurality of light sources that emit light having different wavelengths, and emits light having a wavelength corresponding to the optical disc. A PBS prism having a PBS film, a λ / 4 plate, and a condenser lens are arranged between the light source and the disk. FIG. 5 shows these arrangements.

  The PBS prism 8 is formed by bonding light-transmitting substrates 8a, 8b, and 8c having inclined surfaces inclined with respect to the optical path. A PBS film 8d that transmits P-polarized light and reflects S-polarized light is provided at the interface between the substrates 8a and 8b. A reflective film 8f that reflects incident light is provided at the interface between the substrates 8b and 8c. The λ / 4 plate 10 is made of an anisotropic crystal such as quartz and shifts the phase of transmitted light by λ / 4.

P-polarized light of a predetermined wavelength emitted from the light source enters the PBS prism 8 and passes through the PBS film 8d. The light emitted from the prism 8 is applied to the optical disc D through the λ / 4 plate 10 and the condenser lens 11. The light reflected by the optical disk D passes through the condenser lens 11 and the λ / 4 plate 10 and enters the PBS prism 8. At this time, since the incident light is transmitted through the λ / 4 plate 10 twice during irradiation and reflection of the optical disk D, P-polarized light is converted to S-polarized light. For this reason, the S-polarized light is reflected by the PBS film 8d of the PBS prism 8 and is reflected and emitted by the reflecting film 8f, and is received by a light receiving element (not shown). As a result, information on the optical disc D is read.
Japanese Patent Laid-Open No. 10-143901 (2nd page to 12th page, FIG. 1)

  However, according to the above-described conventional optical pickup device, the PBS prism 8 is provided with the PBS film 8d and the reflective film 8f. For this reason, there has been a problem that the number of manufacturing steps of the PBS prism 8 is large. Further, since the PBS prism 8 needs to be arranged in one predetermined direction, it is necessary to consider the direction when the PBS prism 8 is installed. Accordingly, there is a problem that the number of manufacturing steps of the optical pickup device 1 is large.

  An object of the present invention is to provide a prism that can reduce the number of manufacturing steps, an optical pickup device using the prism, and an optical system.

  In order to achieve the above object, the present invention has first to third transparent members having joint surfaces inclined with respect to two parallel surfaces, and the joint surfaces of the first and second transparent members are the first. In a prism that is bonded via an optical thin film and the bonding surfaces of the second and third transparent members are bonded via the second optical thin film, the first and second optical thin films are arranged in parallel from the PBS film. In addition, the distance between the end face of the first transparent member and the first optical thin film is equal to the distance between the end face of the third transparent member and the second optical thin film.

  According to this configuration, for example, when P-polarized light is incident on the prism, it is transmitted through the first optical thin film and emitted. When S-polarized light is incident, it is reflected by the first optical thin film and the second optical thin film and is emitted. Since the first and second optical thin films made of the same PBS film are arranged at the same distance from both end faces, the prism is formed in point symmetry. The first to third transparent members may be formed by joining a plurality of transparent members.

  According to the present invention, in the prism configured as described above, the first and second optical thin films are formed on the second transparent member, and an adhesive layer is provided between the first and second optical thin films and the first and third transparent members. It is characterized by that. According to this configuration, the light reflected by the first optical thin film and reflected by the second optical thin film proceeds without passing through the adhesive layer.

  Moreover, this invention has the 1st-3rd transparent member which has a joint surface inclined with respect to two parallel surfaces, and adhere | attaches both the said joint surfaces of a 1st, 2nd transparent member through a 1st optical thin film. In the prism in which both the joint surfaces of the second and third transparent members are bonded via the second optical thin film, the first and second optical thin films are formed on the second transparent member and the first and second optical films are formed. An adhesive layer is provided between the thin film and the first and third transparent members. According to this configuration, the light reflected by the first optical thin film and reflected by the second optical thin film proceeds without passing through the adhesive layer.

  Moreover, this invention has a 1st, 2nd transparent member which has a perpendicular | vertical surface and inclined joining surface with respect to one surface, and adhere | attaches the said joining surface of a 1st, 2nd transparent member through an optical thin film. In the prism, the first transparent member has the optical thin film formed on the joint surface and an antireflection film formed on two perpendicular surfaces, and an adhesive layer is provided between the optical thin film and the second transparent member. It is characterized by. According to this configuration, light incident from one of the two perpendicular surfaces of the first transparent member on which the antireflection film is formed is reflected by the optical thin film and emitted from the other. At this time, the light reflected by the optical thin film proceeds without passing through the adhesive layer.

Moreover, this invention has the 1st-3rd transparent member which has a joint surface inclined with respect to two parallel surfaces, and adhere | attaches both the said joint surfaces of a 1st, 2nd transparent member through a 1st optical thin film. In addition, in the optical pickup device including a prism in which both the joint surfaces of the second and third transparent members are bonded via the second optical thin film,
The first and second optical thin films are composed of PBS films provided in parallel, the distance between the end surface of the first transparent member and the first optical thin film, and the distance between the end surface of the third transparent member and the second optical thin film. Are equal.

  In the optical pickup device of the present invention, the first and second optical thin films are formed on the second transparent member, and an adhesive layer is provided between the first and second optical thin films and the first and third transparent members. The S-polarized light incident on the second transparent member is reflected by the first and second optical thin films and emitted from the second transparent member.

Moreover, this invention has the 1st-3rd transparent member which has a joint surface inclined with respect to two parallel surfaces, and adhere | attaches both the said joint surfaces of a 1st, 2nd transparent member through a 1st optical thin film. In addition, in the optical pickup device including a prism in which both the joint surfaces of the second and third transparent members are bonded via the second optical thin film,
The first and second optical thin films are formed on the second transparent member, and an adhesive layer is provided between the first and second optical thin films and the first and third transparent members. The light is reflected by the first and second optical thin films and emitted from the second transparent member.

  Moreover, this invention has a 1st, 2nd transparent member which has a perpendicular | vertical surface and inclined joining surface with respect to one surface, and adhere | attaches the said joining surface of a 1st, 2nd transparent member through an optical thin film. In the optical system including the prism, the first transparent member is a light that is incident on the first transparent member by forming the optical thin film on the joint surface and providing an adhesive layer between the optical thin film and the second transparent member. Is reflected from the optical thin film and emitted from the first transparent member.

  According to the present invention, the same PBS film is provided in parallel between the first and second transparent members and between the second and third transparent members, the distance between the end surface of the first transparent member and the first optical thin film, Since the distance between the end face of the transparent member and the second optical thin film is equal, the first and second optical thin films can be formed in the same film forming process. Therefore, the number of prism manufacturing steps can be reduced. Further, when installing the prism in the optical pickup device, it can be arranged in two directions. Therefore, it is possible to reduce the number of manufacturing steps of the optical pickup device.

  According to the present invention, the first and second optical thin films are formed on the second transparent member of the prism composed of the first to third transparent members joined at the joint surfaces inclined with respect to the two parallel surfaces. Since the adhesive layer is provided between the second optical thin film and the first and third transparent members, the light reflected by the first optical thin film and reflected by the second optical thin film proceeds without passing through the adhesive layer. The loss of the reflected light amount can be reduced.

  Further, according to the present invention, the optical thin film is formed on the first transparent member of the prism formed by joining the first and second transparent members with the surface perpendicular to the one surface and the inclined joint surface, and the optical thin film and the second transparent member are formed. Since the adhesive layer is provided between the members, the light reflected by the optical thin film proceeds without passing through the adhesive layer, and the loss of the reflected light amount can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating an optical pickup device according to an embodiment. The optical pickup device 1 includes light sources 2 and 3 that emit light having different wavelengths. The light sources 2 and 3 are alternatively driven in accordance with the optical disk D, so that the optical disk D is irradiated with light having different wavelengths. As the wavelength of the emitted light from the light sources 2 and 3, blue light of 410 nm band (390 nm to 425 nm) and red light of 650 nm band (630 nm to 690 nm) are used. A near infrared ray in a 780 nm band (740 nm to 820 nm) may be used.

  A dichroic prism 5 is disposed on the optical path of the emitted light from the light sources 2 and 3. The dichroic prism 5 has a dichroic film 5e inclined with respect to the optical path. FIG. 2 shows details of the dichroic prism 5. The dichroic prism 5 is formed by sandwiching a dichroic film 5e between transparent substrates 5a and 5b (first and second transparent members) having two vertical surfaces and inclined surfaces in a plan view. The dichroic film 5e is formed on the slope of the substrate 5a, and an adhesive layer 5g is provided between the dichroic film 5e and the slope of the substrate 5b.

  The dichroic film 5e has characteristics of reflecting blue light and transmitting red light. Accordingly, the light emitted from the light source 2 enters the dichroic prism 5 from the incident surface 5c, is reflected by the dichroic film 5e, and is emitted in the direction of the optical disc D from the output surface 5f. The light emitted from the light source 3 enters the dichroic prism 5 from the incident surface 5d, passes through the dichroic film 5e, and is emitted in the direction of the optical disc D from the output surface 5f. The incident surfaces 5c and 5d and the exit surface 5f are provided with an antireflection film 9 that prevents reflection of light of each wavelength.

  FIG. 4 shows the reflection characteristics of the dichroic prism 5. The vertical axis represents the reflectance (unit:%), and the horizontal axis represents the wavelength (unit: nm). In the figure, A shows this embodiment, and B shows a comparative example. In Comparative Example B, a dichroic film 5e is formed on a substrate 5b having no emission surface, and an adhesive layer 5g is provided between the dichroic film 5e and the substrate 5a.

  According to the figure, since the light reflected from the dichroic film 5e does not pass through the adhesive layer 5g, the reflectance is higher than that of the comparative example B. Therefore, the loss of the amount of reflected light can be reduced by forming the dichroic film 5e on the slope of the substrate 5a and providing the adhesive layer 5g between the slope of the dichroic film 5e and the substrate 5b.

  In FIG. 1, a PBS prism 8, a collimator lens 4, a λ / 4 plate 10, a diffraction element 7, and a condenser lens 11 are arranged between a dichroic prism 5 and a disk D. The PBS prism 8 is formed by bonding light-transmitting substrates 8a, 8b and 8c (first to third transparent members) having inclined surfaces inclined with respect to the optical path, and transmits P-polarized light and reflects S-polarized light. PBS films 8d and 8e (first and second optical thin films) are provided.

  FIG. 3 shows details of the PBS prism 8. The substrates 8a and 8c are formed in a trapezoidal shape in plan view, two surfaces parallel to the optical disk D, end surfaces 8j and 8k perpendicular to the two surfaces, and inclined surfaces 8m and 8n inclined to the two surfaces (bonding) Surface). The substrate 8b is formed in a parallelogram in plan view, and has two surfaces parallel to the optical disc D and two parallel inclined surfaces 8p and 8q (joint surfaces) inclined with respect to the two surfaces. An antireflection film 9 for preventing light reflection is formed on two surfaces of the PBS prism 8 parallel to the optical disk D.

  PBS films 8d and 8e are formed on the inclined surfaces 8p and 8q of the substrate 8b. An adhesive layer 8g is provided between the PBS films 8d, 8e and the inclined surfaces 8m, 8n of the substrates 8a, 8c, and the substrates 8a, 8b, 8c are bonded. Thereby, since the S polarized light reflected by the PBS film 8d and reflected by the PBS film 8e does not pass through the adhesive layer 8g, the loss of the reflected light amount can be reduced as described above. Further, the distance L1 between the end face 8j of the substrate 8a and the PBS film 8d and the distance L2 between the end face 8g of the substrate 8c and the PBS film 8e are formed to be equal.

  In FIG. 1, a collimator lens 4 converts light emitted from light sources 2 and 3 into collimated light. The λ / 4 plate 10 shifts the phase of light by λ / 4, and the light emitted from the light sources 2 and 3 passes when the optical disk D is incident and reflected so that the phase is shifted by λ / 2 and P-polarized light is converted to S-polarized light. The

  The diffraction element 7 is composed of a hologram or the like, and varies the condensing position of the condensing lens 11 according to the wavelength. The condensing lens 11 condenses blue light and red light on the optical disc D. A light receiving element 12 made of a photodiode or the like is provided in the reflection direction of the PBS film 8e of the PBS prism 8.

  In the optical pickup device 1 configured as described above, the P-polarized light of the blue light emitted from the light source 2 is reflected by the dichroic film 5e and guided to the PBS prism 8. The P-polarized light of the red light emitted from the light source 3 passes through the dichroic film 5e and is guided to the PBS prism 8. Incident light from the PBS prism 8 passes through the PBS film 8 d and is converted into collimated light by the collimator lens 4. Then, the light is condensed on the recording surface of the optical disc D by the condenser lens 11 through the λ / 4 plate 10 and the diffraction element 7. At this time, the condensing position of light having different wavelengths is varied by the diffraction element 7 in accordance with the type of the optical disk D.

  The light reflected by the optical disk D passes through the diffraction element 7, the λ / 4 plate 10, and the collimator lens 4 and enters the PBS prism 8. At this time, incident light is converted into S-polarized light because it passes through the λ / 4 plate 10 twice. In the PBS prism 8, S-polarized light is reflected by the PBS film 8 d, reflected by the PBS film 8 e, and received by the light receiving element 12. As a result, even if the type of the optical disk D is different, a signal corresponding to the wavelength used can be captured and read by the light receiving element 12.

  According to the present embodiment, the PBS prism 8 has the PBS films 8d and 8e, and the conventional reflecting film 8f (see FIG. 5) is not provided. Therefore, the PBS films 8d and 8e are formed in the same film forming process. can do. Therefore, the number of manufacturing steps for the PBS prism 8 can be reduced.

  Further, the distance L1 between the end surface 8j of the substrate 8a and the PBS film 8d and the distance L2 between the end surface 8k of the substrate 8c and the PBS film 8e are formed to be equal, and the PBS prism 8 is configured to be point-symmetric. Therefore, the PBS prism 8 can be arranged so as to have the same function even if it is rotated 180 °. Accordingly, two orientations are allowed when the PBS prism 8 is installed in the optical pickup device 1, and the number of manufacturing steps of the optical pickup device 1 can be reduced.

  Further, since the optical thin film formed in the dichroic prism 5 and the PBS prism 8 is arranged so that the reflected light does not pass through the adhesive layer, the loss of the reflected light amount can be reduced. The same effect can be obtained not only in the optical pickup device 1 but also in an optical system using a prism in which a transparent member is bonded via an optical thin film.

  In the present embodiment, blue light and red light are emitted from the light sources 2 and 3, respectively, but light of other wavelengths may be emitted according to the optical disc D. The PBS films 8d and 8e of the PBS prism 8 transmit P-polarized light and reflect S-polarized light. However, the PBS films 8d and 8e may transmit S-polarized light and reflect P-polarized light.

  The present invention is applied to an optical system such as an optical pickup device that reads information such as a CD, a CD-R, a CD-RW, a DVD, a DVD-R, a DVD-RW, a DVD + R, a DVD + RW, a DVD-RAM, a Blu-ray disc, and an HD DVD. Can be used.

The block diagram which shows the structure of the optical pick-up apparatus of embodiment of this invention. The top view which shows the detail of the dichroic prism of the optical pick-up apparatus of embodiment of this invention The top view which shows the detail of PBS prism of the optical pick-up apparatus of embodiment of this invention The figure which shows the reflective characteristic of the dichroic prism of the optical pick-up apparatus of embodiment of this invention A plan view showing a main part of a conventional optical pickup device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical pick-up apparatus 2, 3 Light source 4 Collimator lens 5 Dichroic prism 5a, 5b (1st, 2nd transparent member)
5e Dichroic film 5g Adhesive layer 7 Diffraction element 8 PBS prism 8a-8c Substrate (first to third transparent members)
8d, 8e PBS films (first and second optical thin films)
8f Reflective film 8g Adhesive layer 9 Antireflective film 10 λ / 4 plate 12 Light receiving element D Optical disc

Claims (8)

  The first to third transparent members having joint surfaces inclined with respect to two parallel surfaces, and both the joint surfaces of the first and second transparent members are bonded via the first optical thin film, and the second, In the prism in which both the joint surfaces of the third transparent member are bonded via the second optical thin film, the first and second optical thin films are made of a PBS film provided in parallel, and the end surface of the first transparent member and the first transparent member are A prism characterized in that the distance between the first optical thin film and the distance between the end surface of the third transparent member and the second optical thin film are equal.   The first and second optical thin films are formed on the second transparent member, and an adhesive layer is provided between the first and second optical thin films and the first and third transparent members. Prism.   The first to third transparent members having joint surfaces inclined with respect to two parallel surfaces, and both the joint surfaces of the first and second transparent members are bonded via the first optical thin film, and the second, In the prism in which both the joint surfaces of the third transparent member are bonded via the second optical thin film, the first and second optical thin films are formed on the second transparent member and the first, second optical thin film and the first, A prism comprising an adhesive layer between the third transparent member.   A prism having first and second transparent members each having a surface perpendicular to one surface and an inclined joint surface, wherein the joint surfaces of the first and second transparent members are bonded via an optical thin film. The transparent member has the optical thin film formed on the bonding surface and an antireflection film formed on two perpendicular surfaces, and an adhesive layer is provided between the optical thin film and the second transparent member. . The first to third transparent members having joint surfaces inclined with respect to two parallel surfaces, and both the joint surfaces of the first and second transparent members are bonded via the first optical thin film, and the second, In an optical pickup device including a prism in which both joint surfaces of a third transparent member are bonded via a second optical thin film,
The first and second optical thin films are composed of PBS films provided in parallel, the distance between the end surface of the first transparent member and the first optical thin film, and the distance between the end surface of the third transparent member and the second optical thin film. An optical pickup device characterized by equality.   The first and second optical thin films are formed on the second transparent member, and an adhesive layer is provided between the first and second optical thin films and the first and third transparent members. 6. The optical pickup device according to claim 5, wherein the optical pickup device is reflected by the first and second optical thin films and emitted from the second transparent member. The first to third transparent members having joint surfaces inclined with respect to two parallel surfaces, and both the joint surfaces of the first and second transparent members are bonded via the first optical thin film, and the second, In an optical pickup device including a prism in which both joint surfaces of a third transparent member are bonded via a second optical thin film,
The first and second optical thin films are formed on the second transparent member, and an adhesive layer is provided between the first and second optical thin films and the first and third transparent members. An optical pickup device that is reflected by the first and second optical thin films and is emitted from the second transparent member.   An optical system comprising first and second transparent members each having a surface perpendicular to one surface and an inclined joint surface, and a prism that adheres the joint surfaces of the first and second transparent members via an optical thin film. In the system, the first transparent member has the optical thin film formed on the joint surface and an adhesive layer provided between the optical thin film and the second transparent member, and light incident on the first transparent member is the optical thin film. An optical system that is reflected and emitted from the first transparent member.

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